Actuators for control devices provide an interface for a variety of mechanisms. Often such actuators must not only enable an operator to access the controls with comfort and ease but must also provide a function indicator that is relative to the actuator's position. In addition, many actuators must be capable of displaying such a function indicator in both daylight as well as low ambient light or nighttime conditions. One known and successful approach to providing such a function indicator is through the use of backlighting. Commonly, a clear or translucent material is utilized for the indicator portion while an opaque material is often used for the actuator body. This allows light, from a position behind the actuator, to travel through the clear or translucent material and illuminate the indicator portion.
The appearance and lighting of an actuator can be important to both functionality and convenience. Often, a high contrast indicator is desirable for daylight conditions. Commonly, this takes the embodiment of a white indicator, although a variety of colors or combinations of colors may be desirable. In low ambient light or nighttime conditions, in addition to backlighting, often a different appearance or coloration is desirable. It is known that this dual appearance function may be provided through a variety of methods. The use of multi-shot injection molding to create a clear indicator portion and an opaque base is one common approach. Filtered lamps or colored plastic filter inserts can be positioned behind the actuator to add the dual coloration functions. Often, however, such approaches may contribute undesirable cost, time, and complexity to the manufacture and assembly of the actuator.
One approach to providing both daytime and nighttime functionality is through the use of an applique. Appliques are thin films applied to the actuators, and a variety of other components, that can be screened with decorations in a variety of colors. The appliques may be affixed to the actuator through a variety of methods. One known technique forms the film to the desired shape and then molds the applique to the material. Another technique, using very thin film, loads the films directly into the molds and the indicator material is injected behind it. Through the use of multi-layer screening and, or screening on two sides, appliques provide a practical and cost effective approach to controlling the appearance of the indicator and providing dual lighting characteristics.
Although the use of appliques is clearly beneficial, their use is not always compatible with applicator production techniques. Commonly when an applique is in-molded, or formed and molded to a base part, there is an objectionable line that is visible around the perimeter where the applique ends. In some actuators, such as pushbuttons, the base of the actuator is often recessed behind a mounting plate, and the objectionable witness lines cannot be seen. In other actuators, however, such as knobs, the actuator must extend out farther from its mountings to provide adequate accessibility. In these circumstances, it is often difficult or impractical to hide the objectionable witness lines. In addition, it is often desirable for actuators, such as knobs, to have a soft touch surface. The soft touch films suitable for use as appliqués are commonly not ultra-violent resistant to color change. Many environments, such as use in automotive components, make the use of materials subject to ultraviolet color change unsuitable. The need to utilize the benefits of applique technology without unsightly witness lines, poor UV resistance, and a lack of a soft touch surface has driven technology to the development of appliqué and soft touch over mold combinations.
The use of soft touch actuators can be highly beneficial. The use of rigid material can make it difficult to match the color and texture of the material surrounding the actuator, as in the case of an automotive dashboard. The use of a soft touch material allows the actuator to blend into the dashboard, making it highly desirable from a styling standpoint. One known approach to combining dual light actuators with soft touch characteristics utilizes a translucent base to form the actuator, an appliqué to provide the dual lighting characteristics, and an opaque soft touch overmold to cover the base, with the exception of the indicator portions. This combination results in a cost effective and functional approach to combining soft touch technology with appliqué lighting benefits.
Although the combination of appliqué lighting with over mold technology has served to improve the actuator appearance and function, there is still room for improvement utilizing these technologies. The illumination of the indicator areas, while clearly indicating the actuators functions in dimly lit conditions, may not adequately illuminate the actuator as a whole. This may require the consumer to engage the perimeter of the actuator in such dim conditions by feel. Although this method of interaction accomplishes the task, it may diminish customer satisfaction and serve to undermine the overall ergonomic feel of the controls. It would be more desirable to illuminate the perimeter of the actuator such that the user could confidently grasp it during nighttime operation.
One approach to illuminating the perimeter of the actuator has been to provide illumination from the surface the actuator is mounted on. To benefit from the discussed appliqué/soft touch over mold technologies, this approach requires that similar techniques be applied to the mounting surface as the actuator itself. These additional manufacturing processes can lead to undesirable increases in the complexity and cost of the overall production. It would be far more beneficial to provide perimeter illumination directly from the actuator itself, and thereby reduce the time, cost, and complexity of the overall assembly.